This invention relates to the monitoring of a fluid stream in respect of its contamination content.
An important need to monitor contaminated fluid streams or streams capable of becoming contaminated arises where a fluid is to be discharged to waste so long as it does not unacceptably pollute the environment. One of the less tolerable pollutants is oil, which may be a variable constituent of industrial effluents intended to be discharged into rivers, a variable contaminant of water pumped from ships' bilges and a varying contaminant of sea-water ballast to be discharged from cargo tanks of oil tankers.
It is possible to take a discrete sample of a water stream contaminated with oil and to determine the degree of contamination of the water by the oil. One effective method of operating on a sample to this end involves agitating with the sample a liquid solvent of the oil, allowing the resultant oil/solvent solution to settle from the water and measuring the power of the oil/solvent solution to absorb infra-red radiation. However, so far as we know, this procedure is not capable of being converted otherwise than in a complex way from a process using discrete samples to a continuous process and is in any event not capable of being converted to a continuous process giving instantaneous or nearly instantaneous derterminations so as to make possible useful continuous monitoring of fast-moving partially contaminated fluid streams. Monitoring units have therefore been devised exploiting the property of oil of being excitable into fluorescence, which have allowed of continuous practically instantaneous monitoring of oil-contaminated water streams and have operated very effectively, more particularly for supervising the discharge of sea-water ballast from oil tankers with monitoring of its degree of oil content.